In modern technology, molded-case circuit breakers (MCCBs) are known and are used extensively. Such molded-case circuit breakers make it possible in particular to switch high currents or powers. Since such molded-case circuit breakers are often also formed with fuse apparatuses, such as, for example, an overload fuse and/or a short-circuit fuse, known molded-case circuit breakers also increase safety when switching such currents. In order to provide a current with a high power and/or a high intensity, the current is usually provided in polyphase form with in each case one line per phase.
In the event of the occurrence of a fault, for example an overload or a short circuit, in only one of these phases, however, all phases which are switched by a common molded-case circuit breaker need to be disconnected, however. Such molded-case circuit breakers therefore have a rotor shaft, wherein the rotor shaft is constructed from individual rotor shaft modules. A rotor shaft module is provided for each phase of the current to be conducted, wherein the rotor shaft module has a contact element, which is designed to open and close a conductive connection for the respective phase. The entire switching mechanism of the molded-case circuit breaker, in particular the rotor shaft consisting of rotor shaft modules with the respective contact elements for the individual phases, fixed contacts for each individual phase and the associated mechanism of the molded-case circuit breaker, forms a breaker latching mechanism of the molded-case circuit breaker.
In the case of molded-case circuit breakers, high torques act on the contact system which is formed by the fixed contacts and the contact element for each individual phase owing to the breaker latching mechanism and the current forces occurring. Each contact system of a phase of the molded-case circuit breaker needs to be coupled in electrically insulating fashion to one another. Therefore, it is known from the prior art to produce the individual rotor modules from an electrically insulating material, for example plastics.
However, not all materials are capable of absorbing the forces or torques occurring during tripping of the molded-case circuit breaker and also even the permanent loading by the static forces occurring during operation of the molded-case circuit breaker. It is also possible for thermal loading to occur in the case of high currents or electric powers, which thermal loading impairs the strength of the materials used.
In particular in the case of plastics materials which are electrically insulating and are therefore used as material for the rotor modules, the strength and/or rigidity of the rotor modules can be reduced by an input of heat into the plastics material. Owing to the resultant pressure losses, the contact forces can be reduced and therefore the functional reliability of the molded-case circuit breaker can be endangered.
In accordance with the prior art, it is known to solve these problems in particular by virtue of the provision of lower tolerances of the contours of coupling apparatuses used to connect the individual rotor modules. By virtue of these low production tolerances, in particular in order to avoid pre-existing defects in the connecting apparatus owing to these low tolerances, however, complex measures are required in the manufacture and fitting of the rotor shaft modules of the molded-case circuit breaker.
In order to transfer the rotational forces occurring, such low tolerances are sometimes already necessary in the manufacture of the rotor shaft modules that destruction of a coupling apparatus may arise in the case of only slightly faulty or else only unnoticeable fitting of the rotor shaft modules to a rotor shaft. Furthermore, owing to the use of plastics, the maximum transferable rotational force between the individual rotor shaft modules is limited.
However, this also limits the intensity of the current or the level of the power which can be switched by the molded-case circuit breaker. This is because high currents or high powers also entail high current forces, wherein the resultant higher torques can no longer be safely transferred by the connecting apparatuses between the individual rotor modules of the rotor shaft of the molded-case circuit breaker in the case of tripping of the molded-case circuit breaker, in the worst case scenario. Failure of the molded-case circuit breaker at high currents or high electrical powers can thus not safely be ruled out.